Thermoplastic partial denture clasps have been fabricated with pigmented polyamide/copolymer, polyacetal, which have poor aesthetic properties, and transparent ‘amorphous’ polymer compounds, which results in poor physical properties and require laborious fabrication methods. Amorphous polyamides display a clear and colorless quality however; very high viscosities and poor physical/mechanical properties preclude their use as injection molded dental resins.
Removable partial dental prostheses are employed to restore one or more, but not all, of the natural teeth of a patient. The primary objectives of a properly designed dental prosthesis include the preservation of remaining teeth, along with hard and soft oral tissue, the restoration of oral function, and the restoration of dental and facial aesthetics.
Removable partial dental prostheses are commonly formed with a base or saddle which rests on the oral mucosa in an edentulous space and is coupled by connector means to one or more abutment teeth, that is, a tooth which abuts or is adjacent to the edentulous space.
Perhaps one of the most common forms of partial dental prosthesis is the distal extension removable partial denture which is used to replace posterior teeth with artificial teeth on one or both sides of the mouth. Distal extensions are commonly secured to an abutment tooth by clasps, which are mounted on the abutment tooth to provide for stabilization and retention of the prosthesis, and a connector, which extends between the clasp and the base of the distal extension. The base or saddle of the distal extension rests on the alveolar ridge.
Prefabricated clear and tooth colored thermoplastic clasps are described in U.S. Pat. No. 5,102,337. The prefabricated clasps are contoured by applying heat to the area which the technician wishes to shape and bend. Kulwiec et al. In U.S. Pat. No. 4,412,824 discloses removable partial dental prosthesis and method of forming and supporting the same.
Prior art dental devices have low impact strength. These problems of the prior art are overcome by the present invention. The prior art does not disclose a dental device including thermoplastic polyamide having a Charpy notched impact strength of at least 3.5, or a dental device including polyamide having at least 10 percent by weight of micro-crystals having a largest dimension less than 750 nanometers, as provided by the present invention.